Complex telecommunications systems are often of a modular design. Such systems may have an enclosure housing a printed circuit board (“PCB”) card cage or shelf having card slots with card guides into which a number of differently configured PCBs or PCB cards may be inserted. The card cage typically has a backplane (or midplane) with one or more multi-contact receptacle connectors into which one or more corresponding multi-contact plug connectors on the PCB may be inserted in a pluggable manner. The PCB may have a faceplate attached to an outer facing edge, the faceplate having tabs or handles for grasping to insert and remove the PCB from the card guides, slot, and cage. The faceplate is the part of the PCB assembly that can be seen when the PCB is inserted into a card cage. The faceplate may also function to secure the PCB or PCB card in the card guides or cage.
New generation PCBs for installation in existing (or new) systems are often thinner in design to reduce the aspect ratio of through-board vias, thereby increasing the reliability of the vias. The aspect ratio of a via is the ratio of the length of the via (for a through-board via, this length is the same as the board thickness) to its diameter. Reducing the diameter of vias increases the routability of a PCB. Routability refers to the ease with which traces can be routed through the PCB. Vias can create congestion in routing and larger diameter vias create more congestion which degrades routability. These problems can be offset by reducing the thickness of the PCB, for example, by reducing the number of layers comprising the board.
However, thin PCBs create several problems for existing (or new) systems that are configured for thick PCBs. One problem is that the thin PCBs may not fit securely (i.e., without play) into the card guides of such a system. This play in the fit of the PCB can cause bent connector pins on connectors of the backplane/midplane of the system due to misalignment when the PCB is being inserted into the system's card cage. Another problem is that sensors within the system may fail to detect the presence of a thin PCB plugged into the system if the thin PCB is not properly seated in card guides due to play in the fit of the thin PCB within the guides.
Adapting the card guides of such a system to accommodate thin PCBs is often not practical because any given card slot must be able to accept both the thin and thick PCBs. That is, there needs to be flexibility as to which slots are populated by which PCB types. Furthermore, modifying systems in the field in such a way as to accommodate thin PCBs is time-consuming and expensive.
The above problems are not unique to telecommunications systems. Redesigning PCBs and PCB cards for existing systems to reduce costs, add functionality, etc., is common in a variety of technical fields (e.g., data processing, manufacturing/industrial controls, etc.). Accordingly, several attempts have been made to address these problems. For example, U.S. Pat. No. 6,122,176 to Clements provides a mounting system for easier on-line replacement of odd-sized circuit cards in a card cage. This patent is directed to adapting odd-sized cards to be received in an electronic system. The patent describes a planar frame on which the subject circuit card is mounted. However, the patent does not address the problem of accommodating PCBs of various thicknesses. As another example, U.S. Pat. No. 6,191,950 to Cox, et al., provides a snap-together printed circuit card cover with an integral card support for use with Personal Computer Memory Card International Association (“PCMCIA”) cards of various thicknesses. However, this patent would appear to be restricted to PCMCIA card applications. As another example, U.S. Pat. No. 6,967,850 to Barr, et al., provides a short card support for supporting a short printed circuit card insertable into an electronic system. The short card support has a card guide end adapted to couple to the card guide of the electronic system and a card receptor end adapted to couple with a first edge of the short printed circuit card. A support span between the card guide end and the card receptor end permits the short card support to accommodate varying lengths of short printed circuit cards. The card support is also adjustable for accommodating cards of varying thickness. And, as a final example, United States Patent Application Publication No. 2005/0124180 by Simonovich, et al., provides a removable card guidance block. The guidance block includes a base and a pair of opposing sides. A first set of opposing sides are attached to a top side of the base and provide a first separation configured to accept a first circuit card. A second set of opposing sides are attached to a bottom side of the base and provide a second separation configured to accept a second circuit card. However, these last two patents would appear to require modification to existing card guides or card cage components.
A need therefore exists for adaptors for adjusting the thickness of PCBs for installation in card guides. Accordingly, a solution that addresses, at least in part, the above and other shortcomings is desired.